Something like this is probably going to be your cheapest solution, just get however many you need and stack them up.
If I understand correctly, you’re looking for a receiver that has direct inputs for each amplifier channel, and also has build-in crossover selection as well (presumably full-range capability with high-, low-, and band pass options, based on your stated application of speaker design and development), for each amplifier channel?I basically want a 6 channel amp, that I can use for speaker development with active crossovers, so, if I'm doing a 3 way, I need 6 separate channels I can plug my own 6 source channels into
It doesn’t exist. You will need outboard amplification and an outboard electronic crossover processor, like what RTS linked. Alternately, you could go with late model professional-grade amps that have on-board digital processors.So, how rare is this in AVR's?